Paperboard container with interlocking flap closure



R. E. ACKER July 26, 1955 PAPERBOARD CONTAINER WITH INTERLOCKING FLAP CLOSURE Filed May 14, 1955 2 Sheets-Sheet l R. E. ACKER July 26, 1955 PAPERBOARD CONTAINER WITH INTERLOCKING FLAP CLOSURE Filed May 14, 1953 2 Sheets-Sheet 2 United PAPERBQARD CONTAKYER WITH INTER- LOCKING FLAP CLGSURE Application May 14, 1953, Serial No. 355,077

1 Claim. (Cl. 22939) The improved container comprising the present invention is particularly well adapted for use in connection with the packaging of canned goods, especially in small quantity packaging as, for example, in dozen lots such as has been found desirable for consumer distribution of canned beer. The container of the present invention is however capable of other uses and the same may, with or Without modification, be employed in connection with the packaging of solid articles other than canned goods, or with the packaging of goods in bulk. Irrespective however of the particular use to which the present container may be put, the essential features of the invention are at all times preserved.

The invention in particular relates to a paperboard container having for its bottom closure a series of interlocking closure flaps, each flap being hingedly connected to one of the vertical side walls of the container. The various closure flaps are so designed that they may be interengaged and locked together by a simple inthrusting movement of the flaps after they have initially been folded one over the other in a predetermined order, and such flaps may readily be disengaged by applying pulling force to the outermost flap to release it from its locked position with respect to the other flaps.

Containers with interengaged closure flaps of this general push-lock type have the limitation that such closure cannot readily be used to close an access opening and are therefore usually employed only as a bottom closure since the flaps of a solidly filled container cannot readily be disengaged without cutting by means of a suitable tool due to the rigidity with which the flaps are in terlocked.

The present invention is designed to overcome the above noted limitation by providing an access-opening closure formed of interlocked flaps that present a relatively strong and unyielding composite closure structure from the inside of a solidly filled container and at the same time provide a composite closure structure which can be opened relatively easily by applying outside pulling force to an outermost or overlying flap.

The principal object of the invention is to provide a container closure with a flap arrangement which can be assembled with ease Withoutrequiring glue, staples or other separate securing devices and which will constitute a sturdy bottom closure during transportation of the container and contents, effectively withstanding any tend-- ency to be disengaged due to inside pressure caused by weight of the contents, but which will be easy to disengage by pulling outwardly upon the outermost flap.

Other and more specific objects will become apparent as the description proceeds;

Although the invention .has been illustrated herein in the form of a relatively small paperboard container, it will be understood that the invention is not limited to containers of any particular size or weight of paperboard material.

In the drawings:

Fig. 1 is a plan view of a blank from which a container atent 2313365 Patented July 26, 1955 having the improved bottom closure of the present invention can be constructed;

Fig. 2 is a bottom perspective view of the partially erected container illustrating certain sequential steps that are followed in setting up the bottom closure;

Fig. 3 is a perspective view similar to Fig. 2 illustrating a certain inthrusting operation followed in assembling the parts of the bottom closure;

Fig. 4 is a top perspective view of the container in which portions of the top closure are broken away and other portions thereof are displaced more clearly to reveal the nature of the invention; and

Fig. 5 is a bottom perspective view of the completely set up or erected container.

Referring now to the drawings in detail and in particular to Fig. l, acontainer blank is illustrated as being cut and scored to provide side wall portions 10, 12, 14 and 16 which may be of any suitable length or height commensurate with the particular use to which the container may be put. Since, as illustrated in Fig. 5, the container illustrated herein is in the form of a can container or case for packaging filled cans in dozen lots, the side walls 10 and 14 have a length equal to three can diameters while the walls 12 and 16 have a length equal to four can diameters. The height of the Walls 10, 12, 14 and 16 is equal to the can height. The wall 16 has hingedly secured thereto a glue or stapling flap 18.

Push-lock constructions of the type to which the present invention appertains are primarily useful in closing but one end of a container. This is true because the action required to attain the push-lock action necessarily involves appreciable inward depression or infolding of the several interengaged flaps. Thus, if parallel push-lock constructions are employed on opposite sides of the container and one of them is closed and the container filled, inward depression or infolding of the other would be prevented by the rigidity of the container con tents. Since the nature of the top closure has no bearing upon the bottom closure of the present invention, this top closure has been illustratd as being of conventional form, consisting of closure flaps 20, 22, 24 and 26 respectively hinged to the upper edges of the side walls 10, 12, 14 and 16.

Bottom flaps 28, 30, 32 and 34 constructed in accordance with the principles of the present invention, are hingedly connected to the side walls 10, 12, 14 and 16, respectively thus completing the blank. The blank may be folded into a fiat, tubular, knocked-down configuration with the glue flap 18 adhered by glue or by stapling to the side wall 10 in the usual manner of container manufacture and, when selected for use, the container will be squared up as illustrated in Fig. 2 for subsequent infolding of the bottom closure flaps as shown in Fig. 3; inverting of the partially erected container structure; filling thereof through the top opening; folding and closure of the top flaps 2t), 22, 24 and 26, and final sealing thereof as by means of glue applied to the contacting surfaces of the overlapping flaps. When it is desired to unpack the container it will be inverted so that the composite bottom wall thereof is presented upwardly and the various flaps 28, 3t), 32 and 24 will be unfolded in a manner hereinafter described.

The intermediate bottom closure flaps 28 and 32 are preferably identical in size and shape but each is reversed with respect to the other insofar as its side edges are concerned. These flaps are connected to opposed container sidewalls and arranged to fold inwardly from opposite directions on the bottom of the container. Each of these two flaps is generally triangular, being cut back at an angle slightly greater than 45 to provide an inclined edge 36, but the extended portion of the flap at the free end thereof as indicated at 38, is of rectangular configuration having an edge 40 parallel to the transverse edges of the container blank. The length of each of the flaps 28 and 32 from its juncture with the adjacent side wall 10 or 14, as the case may be, to the outer free edge 42 is preferably somewhat less than one-half the longitudinal extent of the erected container so that when these flaps are folded inwardly to form the container bottom wall their free edges 42 remain spaced from each other, as shown in Fig. 2.

The underlying flap 30 is generally rectangular but it is characterized by the provision of an elongated slot 44 having a substantial portion of one side open as at 46. Another way of describing this arrangement is to state that a wide notch 46 extends inwardly from the free edge 48 of the flap and that the sides of the notch are cut laterally in opposite directions to provide 0ppositely extending short narrow slots 59 in alignment with one another. The flap 30 is scored along diagonal lines as at 52 extending from the slots 50 outwardly and inwardly of the blank in opposite directions as shown.

These score lines 52 may be said to truncate the corners of the flaps, thus leaving bendable, generally triangular corners 53 which perform a special function during opening of the container.

The overlying flap 34 has its sides cut back at an angle slightly less than 45 to provide inwardly inclined side edges 54 which converge outward and terminate at the base of a tongue portion 56 which, if desired, may be delineated from the main body portion of the flap by a score line. The tongue 56 may be formed with rounded edge portions 60, merging with the free edge 62 of the flap.

The free edges 42 of the flaps 28 and 32 and the free edges 48 and 62 of the flaps 30 and 34 respectively, are all in alignment in the blank as shown in Fig. 1. The longitudinal extent of the slot 44 provided in the flap 30 is slightly greater than the longitudinal extent of the tongue 56 of the flap 34 as measured along the free edge 62. The combined heights of the extended portions 38, i. e. their transverse width as measured from the juncture of an inclined edge 36 to the edge 42 plus the intervening distance between the free edges 42 when the latter are opposed in the folded bottom closure assembly, as illustrated in Fi 2, are designed to be slightly less than the length of the tongue 56 measured along its free edge 62. These dimensional features all contribute toward efficient container closing and opening operations as will become clear presently.

In closing the container after the blank of Fig. 1 has been squared, the bottom flap 30 is first folded inwardly and thereafter the flaps 28 and 32 are folded inwardly to lie over the flap 30 as seen in Fig. 2. Finally, the flap 34 is folded inwardly over the previously folded flaps. The structure may then be locked by pressing inwardly on the flap 34 adjacent the free end thereof,

i. e. at the center of the composite closure, so as to depress all of the flaps by an inter-camming action until the outer free edge of the tongue 56 enters slot 44 provided in the flap 31 The inward pressure is then released and all of the flaps will spring back outwardly into locked overlapping contact.

it is to be noted that during the infolding operation just described, the free edge 62 of the tongue 56 will slide on the outer surface of the flap 30 and depress this latter flap throughout a comparatively wide angle. During such camming depression of the flap 30, the flaps 28 and 32 will also be subject to angular depression but to a somewhat lesser extent since these two flaps will receive the camming thrust of the flap 34 from regions of the flap 34 that are considerably removed from the end of the flap. At the precise moment that the tongue 56 enters the slot 44, the flap 30 is out of contact with the two flaps 28 and 32 and it is significant that no pressure whatsoever has been applied to the portions 53 which would tend to bend them out of the plane of the flap 30. These flaps therefore remain rigidly in the plane of the flap.

In the locked position of the bottom closure flaps, illustrated in Fig. 5, the score lines 52 partly underlie the inclined edges 36 of the flaps 23 and 32 so that any internal pressure within the container on the composite bottom closure will act upon the flap 30 to apply or transmit force to the flaps 28 and 32 by a third degree leverage action. These latter flaps 28 and 32 will, in turn, transmit force to the flap 34 by a similar third degree leverage action. Finally, the flap 34 will expend its force on the flap 30 through the tongue 56 but the amount of this force will be appreciably diminished due to the compounded leverage actions referred to. Thus the bottom closure of the present invention is capable of withstanding relatively large internal pressures.

As has previously been stated, the longitudinal extent of the slot 44 is slightly greater than the longitudinal extent of the tongue 56 which is received therein. By such an arrangement, an appreciable amount of diagonal distortion of the various flaps relative to one another may take place with the tongue sliding within the slot to prevent edge-to-edge cutting of the paperboard material or bending of the material due to planar compressional forces being applied thereto.

In opening the container to render the contents thereof accessible, the container is inverted (placed bottom up) so as to assume the directional position shown in Fig, 5 and the medial regions of the overlying edge of the slot 44 of the flap 30 will be flexed outwardly as indicated by the dash-dot line showing of this view in the drawings. Such flexing of the flap 30 will withdraw the portions containing score lines 52 progressively from beneath the edges 36 of the flaps 28 and 32 so that the edges 36 will bear frictionally against the corner portions 53 of the flap 3t) and bend the same out of the plane of the flap. These corner portions may then be pulled progressively edgewise from behind the flaps 28 and 32. As soon as the portions 53 have cleared the edges 36 of the flaps 28 and 32 the remaining flaps are all free of the locking action and opening of the bottom closure may readily be completed.

It has been found that a paperboard container of the character described herein, suitable for use in the packaging of twelve filled cans and which will withstand considerable internal pressure distributed over the interior surface of the composite bottom closure, may be opened in the manner indicated above by the application of a relatively small pulling force applied to the medial region of the edge of the slot 44.

It will of course be understood that, in the manufacture of containers in accordance with the principles of the invention, the blank of Fig. 1 preferably is cut so that, in the case of corrugated paperboard material, the corrugations will extend transversely of the blank. Thus in the locked bottom closure the corrugations of the various fiaps 28, 30, 32 and 34 will extend inwardly from the hinge lines of the flaps toward the center of the closure. Such an arrangement obviously will be conducive toward greater rigidity of the locked structure.

While the present description sets forth a preferred embodiment of the invention, various changes may be made in the construction without departing from the spirit of the invention, and it is therefore desired that the present embodiment be considered in all respects as illustrative and not restrictive, reference being had to the appended claim rather than to the foregoing description to indicate the scope of the invention.

I claim:

In a container of paperboard material including four side wall panels hingedly joined in tubular form and a bottom closure flap hingedly joined to each of said side Wall panels along the lower edge thereof, the improved bottom closure wherein the underlying flap is of substantially uniform width and of a length suflicient so that it extends substantially more than half way across said container, said underlying flap also having its central end portion cut back to a line substantially half way 5' across said container and having short slots extending laterally from said out back portion along said line, there being score lines in said underlying flap diverging from said short slots to its lateral edges at points spaced substantially equal distances from the line of juncture between said underlying flap and its associated side wall panel, the two opposing intermediate flaps have the sides thereof adjacent said underlying flap cut back at an angle slightly greater than 45 to a point slightly more than half way across the width thereof to form rectangular portions at their free ends, and the overlying flap extends substantially more than half way across said container and has its sides cut back at an angle slightly less than 45 to a point substantially half way across said container to form a tongue portion at its end, said tongue portion being engageable over said rectangular portions and beneath said underlying flap to lock said closure With the angular edges of the intermediate flaps crossing said score lines in the underlying flaps, whereby said closure is securely locked if internal pressure of contents or the like is exerted on the portions of said underlying flap defined by the outer edges thereof and the score lines therein and said closure may be opened by a pulling action on the exposed edge of said underlying flap above said tongue portion in the absence of such pressure.

References Cited in the file of this patent 

